Managing General Underwriter (MGU)

A managing general underwriter (MGU) is a firm to which an insurance company grants delegated authority to run a specialized book of business. Under a binding agreement, the MGU can accept and reject risks, set pricing within agreed guidelines, bind coverage, issue policies, and frequently administer premiums and even claims — all in the insurer's name. In effect, the carrier outsources its underwriting for a particular niche to experts who understand that class of risk better than a generalist carrier could, while the insurer retains the actual risk and regulatory responsibility.

An MGU is closely related to a managing general agent; the terms overlap in practice, but "MGU" emphasizes underwriting authority and program management, and MGUs are especially common in complex or hard-to-place lines such as professional liability, cyber, and excess and surplus lines programs. For a small-business buyer, you often never see the MGU by name — you buy through your retail agent — but the MGU is the entity that actually evaluates your risk and prices your niche coverage, which is why specialized programs can offer terms a standard market will not.

A practical nuance: because an MGU acts on behalf of the insurer within its delegated authority, coverage it binds is backed by the carrier that appointed it, not by the MGU itself — so the financial strength and rating of the underlying insurer still govern whether claims get paid. Insurers monitor MGUs closely through audits and loss-ratio triggers, and they can pull or restrict authority if results deteriorate. When buying through a program, it is worth confirming which insurer stands behind the MGU's paper and whether that carrier is admitted or surplus-lines, since that determines your regulatory protections and guaranty-fund status.